A SOx concentration sensor for detecting a SOx concentration in the exhaust gas is known. A usual SOx concentration sensor measures an electromotive force produced when SOx changes into sulfuric acid ion within solid electrolyte, to detect a SOx concentration in the exhaust gas. However, it is difficult for such a SOx concentration sensor for detecting an instantaneous SOx concentration to detect an accurate SOx concentration when the SOx concentration in the exhaust gas is low.
A proposed detector for detecting sulfur components cannot detect an instantaneous SOx concentration but can detect an integrated amount of SOx passing through the exhaust passage during a given period (for example, refer to Japanese Unexamined Patent Publication No. 2008-175623).
The detector for detecting sulfur components comprises a SOx storage portion for storing SOx contained in the exhaust gas, measures a property such as an electric resistance, an volume, a heat capacity or the like of the SOx storage portion changing with the increase of an amount of SOx stored in the SOx storage portion and detects an integrated amount of SOx passing through the exhaust passage during a given period on the basis of the measured property.